Rotating body dynamic quantity measuring device and system

ABSTRACT

A single crystal semiconductor including a Wheatstone bridge circuit formed of an impurity diffusion layer whose longitudinal direction is aligned with a particular crystal orientation is connected to a rotating body. A rotating body dynamic quantity measuring device and a system using the measuring device are fatigue- and corrosion-resistant because of the single crystal semiconductor used and are not easily affected by temperature variations because of the bridge circuit considering a single crystal anisotropy.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation application of application Ser. No.11/352,210, filed Feb. 13, 2006 now abandoned, which claims priorityfrom Japanese patent application JP 2005-035376, filed on Feb. 14, 2005,the contents of which are incorporated herein by reference in theirentirety.

BACKGROUND OF THE INVENTION

The present invention relates to a measuring system to detect dynamicquantities of a rotating body.

Dynamic quantities of a rotating body, particularly torques, haveconventionally been measured by attaching a wire strain gauge to therotating body and measuring a change in a resistance of a fine metalwire of the gauge. However, since a thin film easily develops a highcyclic fatigue, it is difficult for the wire strain gauge to maintainreliability for a long period when used in applications that cause highcyclic deformations, such as measuring strains and torques of rotatingshafts. That is, the wire strain gauge has not been able to be used inapplications that affect human lives and thus require very highreliability, such as automotive drive axels. Further, in forming aWheatstone bridge for temperature correction four wire strain gaugesneed to be attached and their possible peeling and damage pose a problemof a degraded reliability. Also since a metal thin film is easilycorroded, the wire strain gauges could not be used for a long periodunder corrosive environments or environments containing water.

Further, in measuring torques of a rotating body some provisions haveconventionally been made, such as picking up a detected value of thewire strain gauges through wired slipping or preparing circuitsincluding power supply, amplifier and transmission unit and transmittingthe detected value wirelessly. This, however, tends to make the devicecomplex, large and heavy. When it is attached to a shaft, the device caneasily fall because of an increased centrifugal force acting on it.Since shafts easily deflect, various corrective measures, includingre-establishing a balance, need to be taken. That is, although it ispossible to take time and labor to perform test measurements using thewire strain gauges, they cannot safely be used for applications thatrequire reliability. See JP-A-6-301881 for reference.

The present invention therefore provides rotating body dynamic quantitymeasuring system and device capable of restraining some of the problemsdescribed above.

SUMMARY OF THE INVENTION

To solve the above problems, a rotating body dynamic quantity measuringdevice using a semiconductive single crystal impurity-diffused layer isplaced on a rotating body.

With this invention, since a semiconductive single crystal is used, thedevice is not fatigued by a high cyclic load. It is therefore possibleto secure a sufficient reliability for a long period of use. Further,since the device is formed of a single crystal and has no grainboundary, it is not corroded under a corrosive environment, allowing fora highly reliable measurement.

Further, since the rotating body dynamic quantity measuring device usinga single crystal semiconductor is very small and light in weight, if itis attached to a rotating body, it is subjected to only a smallcentrifugal force resulting from its own mass and thus requires nospecial high-strength jointing method, which in turn improvesreliability. The single crystal semiconductor in particular can bemanufactured into a very small size with high precision by using thesemiconductor manufacturing technique. Therefore, there is no need for aprocess to re-establish a shaft balance after the measuring device ismounted.

As for details of this invention, the following descriptions mainlyconcern an example case in which a silicon single crystal is used. It isnoted, however, that any semiconductor crystal can be similarly appliedas long as it has a diamond structure.

This invention can provide a rotating body dynamic quantity measuringdevice and a rotating body dynamic quantity measuring system capable ofcontributing to solving some of the above problems.

Other objects, features and advantages of the invention will becomeapparent from the following description of the embodiments of theinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a measuring system as one embodiment ofthis invention.

FIG. 2 is a schematic view of a rotating body dynamic quantity measuringdevice in the embodiment of this invention.

FIG. 3 is a schematic view of the measuring system in the embodiment ofthis invention.

FIG. 4 is a schematic view of the rotating body dynamic quantitymeasuring device in the embodiment of this invention.

FIG. 5 is a schematic view of the measuring system in the embodiment ofthis invention.

FIG. 6 is a schematic diagram showing a working principle for torquemeasurement.

FIG. 7 is a schematic diagram showing an impurity diffusion layer.

FIG. 8 is a schematic diagram showing a Wheatstone bridge circuit.

FIG. 9 is a schematic diagram showing a relation among a dispersionlayer arrangement in the rotating body dynamic quantity measuringdevice, a crystal axis orientation and coordinate axes in the embodimentof this invention.

FIG. 10 is a schematic diagram showing another relation among adispersion layer arrangement in the rotating body dynamic quantitymeasuring device, a crystal axis orientation and coordinate axes in theembodiment of this invention.

FIG. 11 is a schematic diagram showing still another relation among adispersion layer arrangement in the rotating body dynamic quantitymeasuring device, a crystal axis orientation and coordinate axes in theembodiment of this invention.

FIG. 12 is a schematic diagram showing a further relation among adispersion layer arrangement in the rotating body dynamic quantitymeasuring device, a crystal axis orientation and coordinate axes in theembodiment of this invention.

FIG. 13 is a schematic diagram showing a further relation among adispersion layer arrangement in the rotating body dynamic quantitymeasuring device, a crystal axis orientation and coordinate axes in theembodiment of this invention.

FIG. 14 is a schematic diagram showing a further relation among adispersion layer arrangement in the rotating body dynamic quantitymeasuring device, a crystal axis orientation and coordinate axes in theembodiment of this invention.

FIG. 15 is a schematic diagram showing how the rotating body dynamicquantity measuring device is bonded according to the diffusion layerarrangement in the embodiment of this invention.

FIG. 16 is a schematic diagram showing how the rotating body dynamicquantity measuring device is bonded according to the diffusion layerarrangement in the embodiment of this invention.

FIG. 17 is a schematic diagram showing how the rotating body dynamicquantity measuring device is bonded according to the diffusion layerarrangement in the embodiment of this invention.

FIG. 18 is a schematic diagram showing how the rotating body dynamicquantity measuring device is bonded according to the diffusion layerarrangement in the embodiment of this invention.

FIG. 19 is a schematic diagram showing a relation between an outlinegeometry of a single crystal silicon and a sensitivity in thisinvention.

FIG. 20 is a schematic diagram showing a relation between an outlinegeometry of the single crystal silicon and a sensitivity in thisinvention.

FIG. 21 is a schematic view showing an example of marking formed on thesingle crystal silicon in this invention.

FIG. 22 is a schematic view showing another example of marking formed onthe single crystal silicon in this invention.

FIG. 23 is a schematic view showing an example of marking formed on therotating body dynamic quantity measuring device of this invention.

FIG. 24 is a schematic view showing another example of marking formed onthe rotating body dynamic quantity measuring device of this invention.

FIG. 25 is a schematic view showing a measuring system as one embodimentof this invention.

FIG. 26 is a schematic view showing a measuring system as anotherembodiment of this invention.

FIG. 27 is a schematic view showing a measuring system as a furtherembodiment of this invention.

FIG. 28 is a schematic view showing a measuring system as a furtherembodiment of this invention.

FIG. 29 is a schematic diagram showing how the rotating body dynamicquantity measuring device is bonded according to the diffusion layerarrangement in the embodiment of this invention.

FIG. 30 is a schematic diagram showing how the rotating body dynamicquantity measuring device is bonded according to the diffusion layerarrangement in the embodiment of this invention.

FIG. 31 is a schematic diagram showing how the rotating body dynamicquantity measuring device is bonded according to the diffusion layerarrangement in the embodiment of this invention.

FIG. 32 is a schematic diagram showing how the rotating body dynamicquantity measuring device is bonded according to the diffusion layerarrangement in the embodiment of this invention.

DESCRIPTION OF THE EMBODIMENTS

Now, embodiments of this invention will be described in detail byreferring to the accompanying drawings.

Embodiment 1

FIG. 1 shows a construction of a rotating body dynamic quantitymeasuring system in a first embodiment of this invention. A rotatingbody dynamic quantity measuring device 101 is installed on a surface ofa rotating shaft 12 to measure a torque of the rotating shaft 12 as theshaft 12 rotates about a rotating center 14. The rotating body dynamicquantity measuring device is formed of a single crystal silicon shapedlike a square chip which measures several hundred microns to severalmillimeters in one side and ten microns to several hundred microns inthickness. A back of an element forming surface or a diffusion layer isbonded to the rotating shaft 12 to measure its strains. Normally, inmeasuring the torque of the rotating shaft, a strain gauge formed of ametal foil is used. However, the metal foil used in the strain gauge hasa short fatigue life. So when attached to a rotating shaft thatundergoes high cycle deformations, the metal foil cannot withstand along period of use. A semiconductor, represented by silicon, has asignificantly large yield strength compared with that of common metalfoil strain gauges and thus, when subjected to the same deformation,produces only small plastic deformations, exhibiting a significantlylong fatigue life for high cycle deformations. The semiconductortherefore has an advantage of being able to perform the torquemeasurement stably for a long period. Among strain sensors using asemiconductor there are those using a polycrystalline silicon. Thepolycrystalline silicon has many crystal grain boundaries therein atwhich environmental corrosions easily occur, degrading the measurementaccuracy and causing wire breaks. When a single crystal semiconductor isused for the rotating body dynamic quantity measuring device, since itcontains no grain boundary, the effects of environmental corrosions atgrain boundaries can be eliminated, assuring an excellent reliabilityover a long period of use. As the single crystal semiconductor, a singlecrystal silicon is most desirable because of its advantages of goodmatching with other electric circuits, a large destructive strength andlow cost.

The rotating shaft with a torque measuring function is characterized inthat a single crystal semiconductor chip is used for a torque measuringsensor and that an impurity diffusion layer that constitutes a torquemeasuring element is formed on a silicon substrate 2. FIG. 2 shows therotating body dynamic quantity measuring device 101 of this invention.Here is shown an example case where a single crystal silicon substrate 2is used as the single crystal semiconductor substrate. On the singlecrystal semiconductor substrate 2 constituting the rotating body dynamicquantity measuring device 101, there is formed a torque sensor 1 thatutilizes at least a piezoresistive effect. A back of the substrate,opposite the face where the torque sensor 1 is formed, constitutes abonding surface 3 attached to the rotating shaft 12. The bonding surface3 and the rotating shaft 12 are preferably bonded together using anadhesive. But they may be held together by jointing or fitting. Althoughthe bonding is preferably done over the entire back surface, a part ofthe back surface, such as chip ends, may be left unbonded and still thesimilar effect can be produced though with a slightly increasedmeasuring error. While in this embodiment the back surface opposite theelement forming surface is made a bonding surface, it is also possibleto use the element forming surface for bonding. In that case themeasuring accuracy improves because the element forming surface iscloser to the rotating shaft 12. The rotating body dynamic quantitymeasuring device 101 may comprise, as shown in FIG. 1, a torque sensor 1and pads 4 wired to the torque sensor 1 on the silicon substrate 2, ormay comprise, as shown in FIG. 3, a power supply 5, an amplifier 6, anA/D converter, an analog circuit 8, a communication control unit 9 andan antenna 10 and perform information transfer to and from the outsidecircuit wirelessly. In this case, the power supply 5 may be a battery orself-generate using electromagnetic waves. The wireless communicationwith the external circuits eliminates the need for wiring to and fromthe outside and thus enables the measurement of rotating body dynamicquantities to be performed without interfering with the rotating bodymotion. In the case where the rotating body dynamic quantity measuringdevice 101 of FIG. 3 operates its circuit by using electromagnetic waveenergy from outside, there is no need to provide a separate power supplyunit, substantially reducing its weight, giving rise to an advantagethat when the measuring device is mounted to the rotating shaft 12, arotation balance will not be destroyed. Further, in the rotating bodydynamic quantity measuring device 101 shown in FIG. 3, if an energystorage unit such as a battery is provided, a large instantaneous powercan be produced, allowing the communication distance to be increased.The antenna 10 may be installed on the silicon substrate 2 or, as shownin FIG. 4, outside the silicon substrate 2. When the antenna isinstalled outside, an area enclosed by the antenna can be increased,making it possible to increase the communication distance. Further, asshown in FIG. 5, a highly permeable sheet 31 is placed between theantenna 10 and the rotating shaft 12 to allow for communication withoutside even if the rotating shaft 12 is a metal. In this case, sincethe highly permeable sheet 31 is not interposed between the siliconsubstrate 2 and the rotating shaft 12, the silicon substrate 2 isdirectly attached to the rotating shaft 12 allowing for a highly precisetorque measurement. As described above, different configurations—onewith the torque sensor placed on the silicon substrate, one with thetorque sensor, power supply 5, amplifier 6, A/D converter, analogcircuit 8, communication control unit 9 and antenna 10 installed on thesilicon substrate, and one with the torque sensor 1, power supply 5,amplifier 6, A/D converter, analog circuit 8 and communication controlunit 9 installed on the silicon substrate and with the antenna 10installed outside—have different advantages. These are treated as therotating body dynamic quantity measuring device 101 in the followingdescriptions of this invention.

When a torque is produced in a rotating shaft, a difference in rotatingdegree occurs between the shaft ends, creating a shearing stress τ inthe shaft, as shown in FIG. 6. Thus, the torque produced in the rotatingshaft can be measured by detecting the shearing stress τ.

Silicon has a phenomenon called a piezoresistive effect in which aresistance of the silicon changes when subjected to stresses. Siliconhas a significantly large resistance and thus, as shown in FIG. 7, astress can be measured by doping the silicon with impurities to form animpurity diffused layer, applying a voltage in its longitudinaldirection, and measuring a change in electric current when a stress isproduced. Further, since the resistance of the impurity diffusion layeris strongly influenced by temperature variations, a temperaturevariation correction circuit is required. Normally, in measuring strainsusing a strain gauge, a Wheatstone bridge circuit shown in FIG. 8 isused as a temperature compensation circuit. In that case, the Wheatstonebridge circuit is usually constructed of an active resistor sensitive tothe strains and a dummy resistor insensitive to the strains, with theactive resistor installed on a strain measuring point and the dummyresistor at an isolated point where it is not affected by the strains.

However, if the Wheatstone bridge circuit is used in the rotating bodydynamic quantity measuring device 101 of this invention, all theresistors must be arranged on the silicon substrate 2, in which case allthe resistors are subjected to strains, making it impossible for thebridge circuit to perform its function correctly. In the case of themetal foil strain gauge, a resistance change results from a change incross section of the resistor caused by a strain, so the strain gaugehas a sensitivity only in the longitudinal direction of the resistor.However, in the case of the piezoresistive effect of silicon, a specificresistance changes when the resistor is strained and its magnitude isgreater than the resistance change caused by the change incross-sectional area of the resistor. This means that the strain gaugehas a large sensitivity in other than the longitudinal direction. Thatis, because the strain sensitivity cannot be canceled by using theresistor geometry, a problem remains.

The construction of a bridge circuit of this invention that can solvethis problem is shown in FIG. 9. FIG. 9 represents the bridge circuitusing four resistors of p-type diffusion. The Wheatstone bridge circuit,as described earlier, is required to have an active resistor sensitiveto a dynamic quantity to be measured and a dummy resistor with nosensitivity or which produces an output opposite in sign to that of theactive resistor. That is, the bridge circuit requires an outputdifference between the active resistor and the dummy resistor. Thelarger the output resistance, the greater the sensitivity of the outputof the bridge circuit. As described earlier, silicon has a so-calledpiezoresistive effect in which a natural resistance changes when thesilicon is subjected to strains. Further, in the case of a singlecrystal silicon, the piezoresistive effect has an orthogonal anisotropythat depends on the crystal orientation. That is, by changing arelationship among the silicon crystal orientation, the arrangement ofdiffused resistors and a coordinate system that functions as a referencefor strains, the resistance change with respect to strains can bemanipulated. In FIG. 9, of the four resistors of p-type impuritydiffusion layer making up the Wheatstone bridge circuit, one pair ofopposing resistors is arranged so that its longitudinal direction liesin a [−110] direction of the single crystal silicon and the other pairis arranged so that its longitudinal direction lies in a [110]direction, rotated 90 degrees from the [−110] direction. That is, theWheatstone bridge circuit is so constructed that lines connecting theends 102 of each of half the resistors making up the Wheatstone bridgecircuit lie nearly in the same direction as a <110> direction of thesingle crystal semiconductor but almost perpendicular to those linesconnecting the ends of each of the remaining half of the resistorsmaking up the Wheatstone bridge circuit. Although the first half of theresistors are preferably set almost rectangular to the remaining half,the similar effect can be produced as long as the two groups ofresistors intersect each other at an angle of between 45 degrees and 135degrees. Further, as shown in FIG. 16, a reference coordinate system forstrain is arranged so that its xy coordinate axes, perpendicular to andparallel to the rotating axis, are in a direction almost 45 degrees inrotation from the [−110] direction of the silicon crystal. While theside of the chip is depicted in FIG. 16 to be parallel to the <110>, ifthe direction of the diffusion resistor is <110>, the side of the chipmay be set parallel to <100>. In the embodiments of FIG. 15 and FIG. 16,the diffusion resistors parallel to the [−110] direction have a largesensitivity to the shearing strain τ_(xy) but almost none for otherstrains.

The resistors parallel to the [110] direction have a large sensitivityfor only τ_(xy) and produce an output opposite in sign to that of theresistors oriented in the [−110] direction. That is, the building theWheatstone bridge circuit in the arrangement of FIG. 9 offers anadvantage of being able to measure only the shearing strain τ_(xy) withfour times the sensitivity. In a strain gauge using metal fine wires, ifthere are stresses other than τ_(xy), their influences result inresistance changes. In the rotating body dynamic quantity measuringdevice 101, their influences are very small, assuring a highly precisemeasurement of torque. This advantage, too, is obtained because therotating body dynamic quantity measuring device 101 is formed of asingle crystal silicon and is bonded considering the crystal axisorientation. By arranging this bridge circuit so that the bridge circuitis symmetrical about its center four times on the silicon substrate, asshown in FIG. 9 and FIG. 11, the relationship between the adjoiningresistors can be made equal for all of the four resistors. In forming adiffusion layer of an arbitrary geometry on silicon, etching is used toform that geometry on the mask. To make four resistances equal requiresforming the same geometries on the mask for all the resistors to beformed. During an etching process the density of etching gas on the maskchanges depending on the surrounding environment, greatly affecting theaccuracy of the geometry of the resistors being formed. By forming thediffused resistors in the layout of FIG. 9 and FIG. 11, the influencesof the surrounding environment to which all the four resistors aresubjected can be made equal, so the mask for the four resistors can beetched in the same geometry. Therefore, when the impurity diffusionlayer is formed, it is possible to make the resistances of the fourresistors equal, reduce an offset of the Wheatstone bridge circuit andthereby assure a highly precise measurement of strains. Anotherarrangement in which, as shown in FIG. 10, two resistors are interposedbetween the other opposing resistors, offers an advantage of being ableto reduce an area occupied by the bridge circuit in a case where an areain which to arrange the bridge circuit is limited, as when the siliconsubstrate 2 is made as small as possible to manufacture ainfinitesimally small, rotating body dynamic quantity measuring device101 or when other circuits such as a wireless communication circuit arealso mounted on the silicon substrate 2 as described above.

Although an example case of p-type diffusion layer has been taken up toexplain the method of its arrangement, the similar effect can beproduced if the diffusion layer is an n-type. The rotating body dynamicquantity measuring device 101 using the n-type diffusion layer has anadvantage of a high sensitivity. When the resistors making up the bridgecircuit is an n-type diffusion layer, a pair of opposing resistors is soarranged that, as shown in FIG. 12, its longitudinal direction lies inthe [100] direction of the silicon single crystal and the remaining pairof resistors is so arranged that its longitudinal direction lies in[010] direction, which is 90 degrees in rotation from the [100]direction. That is, the resistors are arranged so that lines connectingthe ends of each of half the resistors making up the Wheatstone bridgecircuit lie nearly in the same direction as a <100> direction of thesingle crystal semiconductor but almost perpendicular to those linesconnecting the ends of each of the remaining half of the resistorsmaking up the Wheatstone bridge circuit. Although the first half of theresistors are preferably set almost rectangular to the remaining half,the similar effect can be produced as long as the two groups ofresistors intersect each other at an angle of between 45 degrees and 135degrees. Further, as shown in FIG. 17 and FIG. 18, the referencecoordinate system for strains is arranged so that its xy coordinateaxes, perpendicular to and parallel to the rotating axis, lie in adirection almost 45 degrees in rotation from the crystal orientation of[100]. In FIG. 17 and FIG. 18, although the sides of the chip are shownto be parallel to <110>, if the direction of the diffusion resistors is<100>, the sides of the chip may be set parallel to <100>. In that case,since the elements other than the diffusion layer can be formed parallelto and perpendicular to <100>, they are not easily affected by thestrains. In the embodiment of FIG. 17, the resistors parallel to the[100] direction have a high sensitivity for the shearing strain τ_(xy)but almost none for other strains. The resistors parallel to the [010]direction also have a high sensitivity for only the shearing strainτ_(xy) but produce an output opposite in sign to the output of theresistors arranged in the [100] direction. That is, by forming aWheatstone bridge circuit in the arrangement of FIG. 9, a sensor can bemanufactured that can measure only the shearing strain τ_(xy) with highprecision. In the case of n-type diffusion layer, too, variations of theresistor geometries during the mask fabrication can be eliminated byarranging the four resistors so that the 4-time symmetric axis of thebridge circuit lies at their center, as shown in FIG. 12 and FIG. 14, asin the case of p-type diffusion layer. This in turn reduces an offset ofthe bridge circuit. Further, when the resistors are arranged as shown inFIG. 13, there is an advantage that the area occupied by the bridgecircuit can be reduced.

In the above arrangement of the impurity diffusion layer that works asresistors, the description that the longitudinal direction lies in the[100] direction means that the direction of a line connecting two viaelectrodes connected to the resistor lies close to the [100] directionand that, when viewed macroscopically, the [100] direction matches thelongitudinal direction. In the path connecting the two via electrodes,the geometry of the diffusion layer may be formed zigzag to increase itsresistance. This applies to both of the n-type impurity and p-typeimpurity.

Although the rotating body dynamic quantity measuring device describedabove resembles the prior art used in pressure sensors when we look atonly the crystal orientation with respect to the longitudinal directionof the diffusion layer, its construction and working principle differentirely from those of the prior art. In the pressure sensor, a hole isformed in a silicon substrate to form a diaphragm and a deformation ofthe diaphragm when subjected to a pressure is detected by a strainsensor formed on the surface of the silicon substrate. That is, localdeformations of the diaphragm due to pressure are detected by two of thefour diffusion layer resistors making up the Wheatstone bridge circuit.The other two diffusion layer resistors are used as dummies and arrangedat a location and in a direction where they are not easily affected bythe deformation of the diaphragm. In this rotating body dynamic quantitymeasuring device, however, since the strain fields to which the fourdiffusion layer resistors in the silicon substrate are subjected aretheoretically the same, it is difficult to manufacture dummy diffusionlayer resistors by utilizing a difference in local deformation as in thepressure sensor. The inventors of this invention have found that theabove arrangement can extract only a shearing stress well only whenmeasuring a torque of a rotating shaft. This has led us to thisinvention. In the case of this invention, unlike the pressure sensor, itis desired that a uniform strain field be generated in the siliconsubstrate. Thus, if there is a hole larger in width than the shorterside of the diffusion layer, as in the pressure sensor, in the back ofthe silicon substrate which is opposite the element forming surface ofthe silicon substrate and which is directly or indirectly placed incontact with an object to be measured, complex strain fields aregenerated in the silicon substrate, which is not desirable. Smallundulations or holes in the back of the silicon substrate may beconducive to an improvement in the adhesion between the object and themeasuring device, but any hole greater in depth than half the thicknessof the silicon substrate will cause complicated strain fields in thesilicon substrate. This is not desirable.

Embodiment 2

The rotating body dynamic quantity measuring device 101 of thisinvention is manufactured by forming minute, thin film structuresseveral microns in size on the silicon substrate several millimeterssquare using the semiconductor fabrication process. So it is difficultto visually identify the diffusion layer in the rotating body dynamicquantity measuring device 101. The sensor of this invention considersthe direction in which a strain is measured, the crystal orientation,and the direction in which the impurity diffused resistors are arranged.Therefore, what matters in the site of actual use of the rotating bodydynamic quantity measuring device 101 is how the device is arranged withrespect to the direction in which a strain is to be taken. So, as shownin FIG. 21, a mark 17 is formed in the rotating body dynamic quantitymeasuring device 101. FIG. 21 shows a rotating body dynamic quantitymeasuring device using a bridge circuit of a p-type diffusion layer onwhich an arrow is marked indicating an axial direction of the shaft. Theuser can make a correct measurement of a torque generated in therotating shaft by arranging the rotating body dynamic quantity measuringdevice so that its arrow is parallel to the center axis of the rotatingshaft. The arrow marking 17 may be formed of thin film or marked withink or paint. The marking may also be dots or line as well as arrow.FIG. 22 shows an example case in which the rotating body dynamicquantity measuring device is manufactured using an n-type impuritydiffusion layer. In the figure an arrow 17 is marked which is parallelto the direction of sides of the silicon substrate 2. The user can takeaccurate measurements of torque by arranging the rotating body dynamicquantity measuring device so that the arrow marking on the device isparallel to the central axis of the rotating body. As shown in FIG. 23and FIG. 24, the arrow representing a direction may be marked on anantenna support portion 11, such as a film, that supports the antenna,rather than on the chip.

Embodiment 3

FIG. 25 shows a third embodiment of the rotating body dynamic quantitymeasuring system according to this invention. FIG. 25 schematicallyshows the rotating shaft 12 as seen from the end, on the circumferentialsurface of which is attached a plurality of rotating body dynamicquantity measuring devices 101 with a wireless communication function.Radio waves transmitted from the rotating body dynamic quantitymeasuring devices 101 are received by a receiving antenna 18 andconverted by a receiving unit 19 into strain and torque values. When therotating shaft 12 is formed of a conductive body such as metal, radiowaves do not easily travel to the far side of the shaft. To cope withthis problem, this embodiment has a plurality of rotating body dynamicquantity measuring devices 101 attached to the circumferential surfaceof the rotating shaft to enable measurement at all times. Thisembodiment offers an advantage that there is no area where strainmeasurements cannot be taken because of the inability to receive radiowaves.

FIG. 26 shows another rotating body dynamic quantity measuring systemaccording to this invention. This embodiment is characterized in thatthe receiving antenna 18 encircles the rotating shaft 12. The radiowaves from the rotating body dynamic quantity measuring device 101 canbe received by the receiving antenna 18 no matter where the measuringdevice 101 is located. This embodiment offers an advantage that there isno area where strain measurements cannot be taken because of theinability to receive radio waves. As shown in FIG. 27, the antenna 10 ofthe measuring device 101 may also be attached to the entirecircumferential surface of the rotating shaft 12. In that case, there isan advantage of facilitating the mounting of the receiving antenna.

FIG. 17 shows still another rotating body dynamic quantity measuringsystem according to this invention. This embodiment represents a casewhere the rotating body is a disk and its shearing strain is measured.The shearing strain of the disk can be measured by the rotating bodydynamic quantity measuring device 101 attached to the surface of thedisk. In addition to the advantage in the torque measurement of arotating shaft, this embodiment offers another advantage that since themeasuring device 101 is very small, measurements can also be taken if anarea of the disk is small. This embodiment is particularly effectivewhere a rotating disk 20 is applied a frictional force by pressingobjects 21 against the disk to block its motion. When, for example, themeasuring device 101 has a pattern of p-type diffusion layer of FIG. 11,the measuring device is arranged so that the circumferential directionof the disk almost matches the <100> crystal axis of the silicon crystalas shown in FIG. 29 and FIG. 30 and that the longitudinal direction ofthe diffusion layer is aligned with the <110> direction. If themeasuring device 101 has a pattern of n-type diffusion layer of FIG. 12,the measuring device is arranged so that the circumferential directionof the disk almost matches the <110> crystal axis of the silicon crystalas shown in FIG. 31 and FIG. 32 and that the longitudinal direction ofthe diffusion layer is aligned with the <100> direction.

The present invention can be applied to devices that measure torques ofrotating bodies.

Some aspects of the invention will be described in conjunction with thedescription of embodiments.

Viewed from a first aspect, the present invention provides a rotatingbody dynamic quantity measuring device comprising: a Wheatstone bridgecircuit formed on an element forming surface, namely, a main surface ofa single crystal semiconductor substrate, the Wheatstone bridge circuitbeing constructed of resistors of a p-type impurity diffusion layer;wherein the resistors are so arranged that lines connecting ends of eachof half the resistors making up the Wheatstone bridge circuit lie nearlyin the same direction as a <110> direction of the single crystalsemiconductor and intersect those lines connecting ends of each of theremaining half of the resistors making up the Wheatstone bridge circuitat an angle of between 45 degrees and 135 degrees; wherein, on a back ofthe single crystal semiconductor substrate opposite the element formingsurface, there is no hole greater in width than a shorter side of thep-type impurity diffusion layer forming the Wheatstone bridge circuit.

A second aspect of the present invention provides a rotating bodydynamic quantity measuring device comprising: a Wheatstone bridgecircuit formed on an element forming surface, namely, a main surface ofa single crystal semiconductor substrate, the Wheatstone bridge circuitbeing constructed of resistors of a n-type impurity diffusion layer;wherein the resistors are so arranged that lines connecting ends of eachof half the resistors making up the Wheatstone bridge circuit lie nearlyin the same direction as a <100> direction of the single crystalsemiconductor and intersect those lines connecting ends of each of theremaining half of the resistors making up the Wheatstone bridge circuitat an angle of between 45 degrees and 135 degrees; wherein, on a back ofthe single crystal semiconductor substrate opposite the element formingsurface, there is no hole greater in width than a shorter side of then-type impurity diffusion layer forming the Wheatstone bridge circuit.

A third aspect of the present invention provides a rotating body dynamicquantity measuring device comprising: a Wheatstone bridge circuit formedon an element forming surface, namely, a main surface of a singlecrystal semiconductor substrate, the Wheatstone bridge circuit beingconstructed of resistors of a p-type impurity diffusion layer; whereinthe resistors are so arranged that lines connecting ends of each of halfthe resistors making up the Wheatstone bridge circuit lie nearly in thesame direction as a <110> direction of the single crystal semiconductorand intersect those lines connecting ends of each of the remaining halfof the resistors making up the Wheatstone bridge circuit at an angle ofbetween 45 degrees and 135 degrees; wherein, on a back of the singlecrystal semiconductor substrate opposite the element forming surface,there is no hole greater in depth than half the thickness of the singlecrystal substrate.

A fourth aspect of the present invention provides a rotating bodydynamic quantity measuring device comprising: a Wheatstone bridgecircuit formed on an element forming surface, namely, a main surface ofa single crystal semiconductor substrate, the Wheatstone bridge circuitbeing constructed of resistors of a n-type impurity diffusion layer;wherein the resistors are so arranged that lines connecting ends of eachof half the resistors making up the Wheatstone bridge circuit lie nearlyin the same direction as a <100> direction of the single crystalsemiconductor and intersect those lines connecting ends of each of theremaining half of the resistors making up the Wheatstone bridge circuitat an angle of between 45 degrees and 135 degrees; wherein, on a back ofthe single crystal semiconductor substrate opposite the element formingsurface, there is no hole greater in depth than half the thickness ofthe single crystal substrate.

A fifth aspect of the present invention provides a rotating body dynamicquantity measuring device according to the first aspect, furtherincluding: an amplification conversion circuit to amplify signals fromthe Wheatstone bridge circuit and convert them into digital signals; atransmission circuit to transmit the converted digital signals to anoutside of the semiconductor substrate; and a power supply circuit tosupply as electricity an electromagnetic wave energy received fromoutside the semiconductor substrate.

A sixth aspect of the present invention provides a rotating body dynamicquantity measuring device according to the second aspect, furtherincluding: an amplification conversion circuit to amplify signals fromthe Wheatstone bridge circuit and convert them into digital signals; atransmission circuit to transmit the converted digital signals to anoutside of the semiconductor substrate; and a power supply circuit tosupply as electricity an electromagnetic wave energy received fromoutside the semiconductor substrate.

A seventh aspect of the present invention provides a rotating bodydynamic quantity measuring device according to the first aspect, furtherincluding: a conversion circuit to amplify signals from the Wheatstonebridge circuit and convert them into digital signals; a transmissioncircuit to transmit the converted digital signals to an outside of thesemiconductor substrate; and a power supply circuit to supplyelectricity to these circuits, the electricity being derived from atleast one of a sunlight, a temperature difference, an inducedelectromotive force and a battery received from outside thesemiconductor substrate.

An eighth aspect of the present invention provides a rotating bodydynamic quantity measuring device according to the second aspect,further including: a conversion circuit to amplify signals from theWheatstone bridge circuit and convert them into digital signals; atransmission circuit to transmit the converted digital signals to anoutside of the semiconductor substrate; and a power supply circuit tosupply electricity to these circuits, the electricity being derived fromat least one of a sunlight, a temperature difference, an inducedelectromotive force and a battery received from outside thesemiconductor substrate.

An ninth aspect of the present invention provides a rotating bodydynamic quantity measuring device according to any one of the first toeighth aspects, wherein the impurity diffusion layer is configured andarranged in nearly a four-time symmetry.

A tenth aspect of the present invention provides a rotating body dynamicquantity measuring device according to any one of the first to eighthaspects, wherein the impurity diffusion layer is configured and arrangedin nearly a mirror symmetry.

An eleventh aspect of the present invention provides a rotating bodydynamic quantity measuring device according to any one of the first totenth aspects, wherein a visible marking representing an axial directionor circumferential direction of a rotating shaft is provided on theelement forming surface of the semiconductor substrate.

A twelfth aspect of the present invention provides a rotating bodydynamic quantity measuring device according to any one of the first totenth aspects, wherein a bonding portion to be attached to an objectbeing measured is formed on a back of the single crystal semiconductorsubstrate opposite the main surface.

A thirteenth aspect of the present invention provides a rotating bodyhaving a dynamic quantity measuring unit of a rotating body dynamicquantity measuring device attached to a surface thereof, wherein thedynamic quantity measuring unit includes a single crystal semiconductorhaving an impurity diffusion layer formed in a surface thereof and aback of the single crystal semiconductor opposite the surface formedwith the impurity diffusion layer is attached to the rotating body.

A fourteenth aspect of the present invention provides a rotating bodyaccording to the thirteenth aspect, wherein the dynamic quantitymeasuring unit includes a single crystal semiconductor having a p-typeimpurity diffusion layer formed in a surface thereof and a <100>direction of the single crystal semiconductor formed with the p-typeimpurity diffusion layer is almost parallel to a rotating axis of therotating body.

A fifteenth aspect of the present invention provides a rotating bodyaccording to the thirteenth aspect, wherein the dynamic quantitymeasuring unit includes a single crystal semiconductor having an n-typeimpurity diffusion layer formed in a surface thereof and a <110>direction of the single crystal semiconductor formed with the n-typeimpurity diffusion layer is almost parallel to a rotating axis of thebody.

A sixteenth aspect of the present invention provides a rotating bodyattached with the rotating body dynamic quantity measuring device of thefirst, third, fifth, seventh, thirteenth or fourteenth aspect, wherein arotating axis direction of the rotating body is almost parallel to a<100> direction of the single crystal semiconductor.

A seventeenth aspect of the present invention provides a rotating bodyattached with the rotating body dynamic quantity measuring device of thesecond, fourth, sixth, eighth, thirteenth or fifteenth aspect, wherein arotating axis direction of the rotating body is almost parallel to a<110> direction of the single crystal semiconductor.

A eighteenth aspect of the present invention provides a rotating bodydynamic quantity measuring system having a dynamic quantity measuringunit of a rotating body dynamic quantity measuring device attached to arotating body, wherein dynamic quantity data measured by the dynamicquantity measuring unit and converted into electromagnetic waveinformation is received by an antenna and a receiving unit to detect thedynamic quantities of the rotating body; wherein the dynamic quantitymeasuring unit includes a single crystal semiconductor having animpurity diffusion layer formed in a surface thereof and a back of thesingle crystal semiconductor opposite the surface formed with theimpurity diffusion layer is attached to the rotating body.

A nineteenth aspect of the present invention provides a rotating bodydynamic quantity measuring system according to the eighteenth aspect,wherein the dynamic quantity measuring unit includes a single crystalsemiconductor having a p-type impurity diffusion layer formed in asurface thereof and a <100> crystal axis of the single crystalsemiconductor formed with the p-type impurity diffusion layer is almostparallel to a rotating axis of the rotating body.

A twentieth aspect of the present invention provides a rotating bodydynamic quantity measuring system according to the eighteenth aspect,wherein the dynamic quantity measuring unit includes a single crystalsemiconductor having a p-type impurity diffusion layer formed in asurface thereof and a <110> crystal axis of the single crystalsemiconductor formed with the p-type impurity diffusion layer is almostparallel to a rotating axis of the rotating body.

A twenty first aspect of the present invention provides a rotating bodydynamic quantity measuring system according to any one of the eighteenthto twentieth aspects, wherein a plurality of rotating body dynamicquantity measuring devices are installed on one rotating shaft.

A twenty second aspect of the present invention provides a rotating bodydynamic quantity measuring system according to any one of the eighteenthto twentieth aspects, wherein an antenna is wound around more than halfa circumference of a rotating shaft.

A twenty third aspect of the present invention provides a rotating bodydynamic quantity measuring system according to any one of the eighteenthto twentieth aspect, wherein a receiving antenna is arranged to covermore than half a circumference of a rotating shaft.

A twenty fourth aspect of the present invention provides a rotating bodydynamic quantity measuring system according to the eighteenth aspect,wherein the rotating body is a disk, the dynamic quantity measuring unitincludes a single crystal semiconductor having a p-type impuritydiffusion layer formed in a surface thereof, and a <100> crystal axis ofthe single crystal semiconductor formed with the p-type impuritydiffusion layer almost matches a circumferential direction of the disk.

A twenty fifth aspect of the present invention provides a rotating bodydynamic quantity measuring system according to the eighteenth aspect,wherein the rotating body is a disk, the dynamic quantity measuring unitincludes a single crystal semiconductor having an n-type impuritydiffusion layer formed in a surface thereof, and a <110> crystal axis ofthe single crystal semiconductor formed with the n-type impuritydiffusion layer almost matches a circumferential direction of the disk.

It should be further understood by those skilled in the art thatalthough the foregoing description has been made on embodiments of theinvention, the invention is not limited thereto and various changes andmodifications may be made without departing from the spirit of theinvention and the scope of the appended claims.

1. A rotating body having a dynamic quantity measuring device saiddynamic quantity measuring device comprising: a Wheatstone bridgecircuit having strain sensors and dummy resistors on a [001] surface ofa single crystal silicon substrate, wherein said strain sensors eachcomprising an area having p type impurity diffusion layer in the siliconsubstrate and a longitudinal direction thereof is the same direction asa <110> direction of the silicon substrate, said dummy resistors eachcomprising an area having p type impurity diffusion layer in the siliconsubstrate and a longitudinal direction thereof is at 90 degrees to thelongitudinal direction of said strain sensor, and a <100> crystal axisof said single crystal silicon substrate substantially matches thecircumferential direction of said rotating body.
 2. A rotating bodyaccording to claim 1, wherein a visible marking representing acircumferential direction of said rotating body is provided on anelement forming surface of said single crystal silicon substrate.